1. Field of the Invention
The present invention relates to a cell station and personal stations in a digital radio communication system.
2. Description of the Related Art
In recent years, a digital radio communication system between the cell station (CS) and personal stations (PSs) using TDMA/TDD (Time Division Multiple Access/Time Division Duplex) techniques is being developed.
The PSs are portable. Therefore, they are carried not only to areas of good wave conditions but also to areas of bad wave conditions. Bad wave conditions correspond to, for example, areas which overlap with other CS's radio zone, and areas where direct waves and indirect waves created by reflections from buildings interfere with each other. Since PSs are carried between areas of good wave conditions and bad wave conditions, normally, a transmit control procedure is applied for error correction/detection control and re-transmit control for transmit errors. In the conventional digital radio communication system, transmit control procedure is applied between the PS at a sender's end and the CS, and between the CS and the PS at a receiver's end. For example, LAPDC (Link Access Procedure for Digital Cordless) is used in PHS (Personal Handy Phone System). This LAPDC is a communication protocol which corresponds to layer 2 of the OSI reference model, using the sub set of HDLC (High-level Data Link Control Procedure). By using the communication protocol like this, reliability of data sending and receiving can be more enhanced. That's because when LAPDC and HDLC are applied, the CS and the PSs can cope with transmit errors by a correction function and a re-sending control function.
According to the conventional art, the digital radio communication system can ensure, by the communication protocol, the reliability of data sending and receiving even though the wave condition is bad. However, in areas of good wave condition, speed of the communication decreases since some processing for using the communication protocol is needed. Specifically, the communication protocol is applied between the PS at the sender's end and the CS, and between the CS and the PS at the receiver's end. So while the data is sent from the PS at the sender's end to the PS at the receiver's end, delay time is generated for the protocol processing at the CS. The speed of the communication is sacrificed by using the communication protocol even in areas of good wave condition.